1. Field of the Invention
This invention relates generally to bicycles and particularly to those having multiple sprocket chain drive systems used in off-road cycling, or mountain biking.
2. Description of the Related Art and Summary of the Invention
The sport of cycling has proven to be an extremely popular and long lasting sport and recreational activity. Through the years, a variety of cycling or biking activities have been pursued by a wide range of participants. Not surprisingly, participants in the various cycling or biking activities and recreations have been operative in a variety of environmental circumstances ranging from high speed competition to slow and casual pleasure riding or cycling. In recent years an interesting type of cycling has emerged which is generally referred to as off-road biking or mountain biking. In this sport activity, participants often ride over extremely rough terrain and challenging hill and mountain trails.
This activity subjects the bicycle and its operative apparatus to extremes in stress, loading and impact. To meet the need for bicycles capable of operating in such high stress and high load environments over such challenging terrain, practitioners in the art have endeavored to provide bicycles which are extremely strong and durable. A competing interest in the production of such strong and durable bicycles is the concurrent need to maintain a substantially light-weight bicycle in order to reduce the energy required to pedal such bicycles across the often hilly and challenging terrain. Toward this end, the typical off-road bicycle utilizes an extremely light-weight frame often fabricated from light-weight exotic metals such as titanium, aluminum and magnesium as well as various high strength alloys thereof. To improve the impact or shock absorption characteristic required to assure sufficient durability and strength of such off-road bicycles, the frame is often fabricated of a plurality of frame portions coupled together using a variety of spring loaded and shock absorbing suspension components. The objective is to provide a frame capable of absorbing substantial impact shock while reducing the energy imparted to the frame through multiple articulated shock absorbing suspension components. The overall objective is, of course, to avoid damage to the light-weight high-strength frame.
Most off-road bicycles utilize chain drive apparatus in which a plurality of varying diameter sprockets are grouped at the rear wheel and are driven by a pedal crank and chain sprocket drive mechanism. A variety of gear ratios or drive ratios are obtained by the use of a chain derailleur mechanism which is operative to transfer the power coupling chain between the various drive sprockets. In this way, the overall drive ratio between the crank and the rear wheel may be varied to allow the user to address; different terrain conditions.
While the multiple sprocket train drive systems in use have been refined to provide extremely effective operation and a wide range of drive ratios to a aid the cyclist introverting challenging hills and trails, a problem often arises due to the combined effect of the flexing shock-absorbing frame and the chain drive system. This problem is known generally as xe2x80x9cchain-whippingxe2x80x9d and arises as the articulated frame portions flex to absorb impact and as the loading upon the chain drive is varied in different circumstances. The end result is the creation of undesired slack within the drive chain allowing the upper and lower spans of the drive chain to whip up and down and disengage from the front drive sprocket. Drive chain whipping action is more severe in the upper span of the drive chain (the portion between the rear sprocket and the upper edge of the chain ring) than in the lower span of the drive chain (the portion between the rear sprocket and the lower edge of the chain ring). This results from the tendency of the derailleur mechanism to maintain greater tension in the lower span.
Drive chain disengagement can be extremely vexing to a cyclist and under (competitive conditions can cause the cyclist to lose his or her ability to effectively compete. Typically, once the drive chain has disengaged from the front sprocket, or chain ring, the cyclist is required to stop and reset the chain upon the chain ring before continuing. In addition, the sudden release of resisting load caused by the chain skipping from the chain ring also creates the possibility of injury to the rider.
In addition to preventing chain disengagement, it is desirable to provide a chain guide apparatus that prevents the chain from jamming between the chain ring and portions of the chain guide apparatus. Furthermore, because riders of mountain bikes often desire to utilize different size chain rings to suit different riding conditions, it is desirable to provide a chain guide apparatus that is capable of accommodating a variety of chain ring sizes, without requiring adjustment or modification of the apparatus.
Accordingly, it is one goal of the preferred embodiments to provide an improved chain drive system for bicycles. It is a more particular goal to provide an improved chain drive system for bicycles in which the problems of chain-whipping at the front drive sprocket are substantially reduced or eliminated. It is also desired to provide an improved chain guide apparatus which is easily installed and capable of preventing jamming of the drive chain when used with different sized chain rings, without the need to modify or interchange components of the apparatus.
In accordance with a preferred embodiment there is provided a chain guide apparatus for use with a bicycle drive system having a pedal crank, a chain ring rotated thereby, a frame supporting the pedal crank and a drive chain engaging the chain ring. The chain guide apparatus comprises an outer bash guard, an inner bash guard and a first guide extending between the outer and inner bash guards. The first guide substantially entirely surrounds a channel, which is sized and shaped to receive a drive chain. The first guide also defines an inner portion, an outer portion, a first connecting portion extending between the inner portion and outer portion and a second connecting portion extending between the inner portion and the outer portion. The first connecting portion is configured to limit downward movement of at least a portion of the drive chain within the channel and defines the radially innermost connecting edge of the first guide. The radially innermost connecting edge of the guide is separated from the chain ring by a first radial distance equal to at least twice the height of the drive chain.
In accordance with a preferred embodiment there is provided a chain guide apparatus for use with a bicycle drive system having a pedal crank, a chain ring rotated thereby, a frame supporting the pedal crank and a drive chain engaging the chain ring. The chain guide apparatus comprises an outer bash guard, an inner bash guard and a first guide extending between the outer and inner bash guards. The first guide substantially entirely surrounds a channel, which is sized and shaped to receive a drive chain. The first guide also defines an inner portion, an outer portion, a first connecting portion extending between the inner portion and outer portion and a second connecting portion extending between the inner portion and the outer portion. The first connecting portion is configured to limit downward movement of at least a portion of the drive chain within the channel and defines the radially innermost connecting edge of the guide. The radially innermost connecting edge of the guide is separated from the chain ring by a first radial distance equal to at least the length of a link of the drive chain.
In accordance with a preferred embodiment there is provided a chain guide apparatus for use with a bicycle drive system having a pedal crank, a chain ring rotated thereby, a bicycle frame supporting the pedal crank and a drive chain engaging the chain ring. The chain guide apparatus comprises an outer frame, an inner frame and a first guide extending between the outer and inner frames. The outer frame is mountable to at least one of a crank spider and a chain ring defining a crank axis. The first guide defines a channel, which is sized and shaped to receive a drive chain. The first guide also defines a first connecting portion extending between the inner portion and outer portion and a second connecting portion extending between the inner portion and the outer portion. The first connecting portion is configured to limit downward movement of a portion of the drive chain within the channel. The second connecting portion is configured to limit upward movement of a portion of the drive chain within the channel. The first connecting portion defines the radially innermost connecting edge of the first guide. The radially innermost connecting edge is located at least a first radial distance from a first point. The first point is located at least a second radial distance from the crank axis. The first radial distance is at least 0.865 inches and the second radial distance is less than approximately 7.299 inches.
In accordance with a preferred embodiment there is provided a chain guide apparatus for use with a bicycle drive system having a pedal crank, a chain ring rotated thereby, a frame supporting the pedal crank and a drive chain engaging the chain ring. The chain guide apparatus comprises an outer bash guard defining a first plane, an inner bash guard defining a second plane and a first guide extending between the outer and inner bash guards. The first guide defines a channel, which is sized and shaped to receive a drive chain. The first guide also defines a first connecting portion extending between the first plane and the second plane. The first connecting portion is configured to limit downward movement of a portion of the drive chain within the channel. The first guide defines a second connecting portion extending between the first plane and the second plane. The second connecting portion is configured to limit upward movement of a portion of the drive chain within the channel. The first connecting portion defines the radially innermost connecting edge of the guide. The radially innermost connecting edge of the guide is separated from the chain ring by a first radial distance equal to at least twice the height of the drive chain.
In accordance with a preferred embodiment there is provided a chain guide apparatus for use with a bicycle drive system having a pedal crank, a chain ring rotated thereby, a frame supporting the pedal crank and a drive chain engaging the chain ring. The chain guide apparatus comprises an outer bash guard defining a first plane, an inner guard defining a second plane and a first guide extending between the outer and inner bash guards. The first guide defines a channel, which is sized and shaped to receive a drive chain. The first guide also defines a first connecting portion extending between the first plane and the second plane. The first connecting portion is configured to limit downward movement of a portion of the drive chain within the channel. The guide defines a second connecting portion extending between the first plane and the second plane. The second connecting portion is configured to limit upward movement of a portion of the drive chain within the channel. The first connecting portion defines the radially innermost connecting edge of the guide. The radially innermost connecting edge of the guide is separated from the chain ring by a first radial distance equal to at least the length of a link of the drive chain.
In accordance with a preferred embodiment there is provided a chain guide apparatus for use with a bicycle drive system having a pedal crank, a chain ring rotated thereby, a bicycle frame supporting the pedal crank and a drive chain engaging the chain ring. The chain guide apparatus comprises an outer frame defining a first plane, an inner frame defining a second plane and a first guide extending between the outer and inner frames. The outer frame is mountable to at least one of a crank spider and a chain ring defining a crank axis. The first guide defines a channel, which is sized and shaped to receive a drive chain. The first guide also defines a first connecting portion extending between the inner portion and outer portion and a second connecting portion extending between the inner portion and the outer portion. The first connecting portion is configured to limit downward movement of a portion of the drive chain within the channel. The second connecting portion is configured to limit upward movement of a portion of the drive chain within the channel. The first connecting portion defines the radially innermost connecting edge of the guide. The radially innermost connecting edge is located at least a first radial distance from a first point. The first point is located at least a second radial distance from the crank axis. The first radial distance is at least 0.865 inches and the second radial distance is less than approximately 7.299 inches.
In accordance with a preferred embodiment, a bicycle is provided. The bicycle includes a drive system having a pedal crank. A frame supports the pedal crank and a chain ring is rotated thereby. A drive chain engages the chain ring. A chain guide apparatus is also provided which includes an outer bash guard, an inner bash guard, and a first guide extending between the outer and inner bash guard. A first guide substantially entirely surrounds a channel, which is sized and shaped to receive a drive chain. The said first guide defines an inner portion, an outer portion, a first connecting portion extending between the inner and outer portion and a second connecting portion extending between the inner and outer portion. The first connecting portion is configured to limit downward movement of a portion of the drive chain in the channel and defines the radially innermost connecting edge of the first guide. The radially innermost connecting edge of the first guide is separated from the chain ring by a first radial distance equal to at least twice the height of the drive chain.